Martin Marietta Materials, Inc. (MLM)

Haulage quickly costs more than the stone itself, so a quarry serves a limited radius and within it faces almost no competition. Permitting a new quarry near a city is close to impossible — that regulatory barrier is the main protection of existing assets, and buying a working quarry is cheaper than opening one.

Demand comes from road and infrastructure building, which is funded by government programmes and is therefore steadier than housing. Profit grows above all through annual price increases per tonne that outpace inflation, since volumes depend on other people's budgets. Risks: fuel, labour costs and a pause in infrastructure spending. The company pays a dividend.